Low profile multi-lens tir

ABSTRACT

In one aspect, an optical lens assembly (herein referred to also as an optic) is provided that comprises a plurality of lenses (or lens segments) adapted to receive light from a light source, each of said lenses (or lens segments) having an input surface and an output surface and a lateral surface extending between the input and output surfaces. The lenses are arranged relative to one another and positioned relative to the light source such that each of the lenses receives at its input surface a different portion of light emitted by the source, e.g., each lens receives at its input surface light emitted by the source into an angular subtense (solid angle) different than an angular subtense associated with another lens. Each lens (or lens segment) guides at least a portion of the received light to its output surface via reflection, e.g., via total internal reflection (TIR).

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/955,839, filed Jul. 31, 2013, which claims the benefit of andpriority to U.S. Provisional Application No. 61/809,631, filed Apr. 8,2013 and U.S. Provisional Application No. 61/678,781, filed on Aug. 2,2012. The entire teachings of these earlier applications areincorporated by reference herein.

BACKGROUND

The present invention is generally directed to a lens assembly, andparticularly to a lens assembly in which a plurality of lenses collimatelight received from a light source via total internal reflection (TIR)as well as optical systems employing such a lens assembly.

In many lighting applications, the light source, e.g., a light emittingdiode (LED), can be large. The use of large traditional TIR lenses tocollimate light from such large light sources can be problematic. Forexample, manufacturing such TIR lenses, e.g., via molding, can bedifficult. Further, many lighting applications can impose spatialconstraints that can render the use of such traditional TIR lensesimpractical.

Accordingly, there is a need for improved lenses, optics and lensassemblies for redirecting, e.g., collimating, light emitted by a lightsource, particularly a large light source.

SUMMARY

In one aspect, an optical lens assembly (herein referred to also as anoptic) is provided that comprises a plurality of lenses (or lenssegments) adapted to receive light from a light source, each of saidlenses (or lens segments) having an input surface and an output surfaceand a lateral surface extending between the input and output surfaces.The lenses are arranged relative to one another and positioned relativeto the light source such that each of the lenses receives at its inputsurface a different portion of light emitted by the source, e.g., eachlens receives at its input surface light emitted by the source into anangular subtense (solid angle) different than an angular subtenseassociated with another lens. Each lens (or lens segment) guides atleast a portion of the received light to its output surface viareflection, e.g., via total internal reflection (TIR).

In some embodiments, the lenses are arranged relative to one another andthe light source such that they collectively receive at least about 80percent, or at least about 90 percent, or 100 percent, of the lightenergy emitted by the source.

In some embodiments, at least one of the lenses in configured tocollimate the light it receives from the light source. In someembodiments, all of the lenses are configured to collimate the lightthey receive from the light source.

In some embodiments, each of the lenses is rotationally symmetric aboutan optical axis. In some embodiments, the optical axis of the lenses cancoincide with an optical axis of the light source. In some otherembodiments, the optical axis of the lenses can be offset relative to anoptical axis of the light source.

In some embodiments, the plurality of lenses comprises an inner lens, amiddle lens, and an outer lens.

In some embodiments, at least a portion of the lateral surface of atleast one of the lenses is separated by an airgap from at least aportion of the lateral surface of an adjacent lens. As discussed in moredetail below, such an airgap can allow redirection, via TIR, of thelight incident on those portions of the lateral surfaces. In such cases,the lateral surface can be configured in a manner known in the art suchthat the incident light (or a substantial portion thereof) is incidenton the surface at an angle that exceeds the critical angle associatedwith the interface between the lens body and air so as to cause totalinternal reflection of the incident light. In some embodiments, at leastone of the lenses includes a lateral surface configured to redirectlight incident thereon via specular reflection. For example, at least aportion of such a lateral surface can be metalized, e.g., via a metallayer having a thickness in a range of about 10 micrometers to about 100micrometers, to cause specular reflection of light incident thereon.

In some embodiments, the lateral surface of at least one of the lensesincludes two portions forming a non-zero angle, e.g., an acute angle,relative to one another.

In some embodiments, the optical lens assembly can exhibit an aspectratio, as defined below, that is equal to or less than about 1, e.g., ina range of about 0.1 to about 1.

In some embodiments, at least one of the lenses (or the lens segments)includes input surfaces with the input surface configured to besubstantially orthogonal to light rays it receives from the lightsource. In some embodiments, a central lens (or lens segment) caninclude a curved surface for collimating the received light viarefraction. In some embodiments, at least one, or all, of the outerlenses surrounding the central lens an include a concave input surfaceconfigured as a section of a putative sphere centered on the lightsource.

In related aspects, the plurality of lenses are removably andreplaceably coupled to one another. For example, in some embodiments,each of the lenses is selectively removable and replaceable independentof the other lenses.

In some aspects, the optical lens assembly can further comprise a lenscap configured to receive light from one or more of the output surfacesof the plurality of lenses and from the light source. In someembodiments, the cap includes a textured surface, e.g., a plurality ofmicrolenses.

In some embodiments of the above optical lens assembly, the lenses arefixedly coupled to one another with each lens at least partiallydisposed in a cavity of an adjacent outer lens. In some suchembodiments, at least one of the lenses includes an annular shoulderseated in an annular recess of an outer adjacent lens such that alateral surface of that lens is separated by a gap from a respectivelateral surface of the outer adjacent lens. In some embodiments, theoptical lens assembly can further include a retaining ring for fixatingthe lenses in a defined relationship relative to one another.

In further aspects, an optical system is disclosed, which comprises alight source, and an optical lens assembly that is coupled to the lightsource to receive light therefrom. The optical lens assembly includes acentral lens, and a plurality of outer lenses disposed about the centrallens, where the lenses of the optical lens assembly are arrangedrelative to one another and relative to the light source such that eachlens receives light emitted by the source into a different angularsubtense.

In some embodiments, the outer lenses are annulus-shaped lenses thatcircumferentially surround the central lens at progressively increasingradial distances from the central lens. In some embodiments, a lateralsurface of each of the lenses is separated by a gap from a lateralsurface of an adjacent lens.

In some embodiments, the lenses can be removably and replaceably coupledto one another. In some embodiments, each lens can be selectivelyremoved and replaced independent of the other lenses.

In some embodiments of the above optical system, the optical lensassembly can have an aspect ratio in a range of about 0.1 to about 1.

In some embodiments, in the above optical system, the optical lensassembly is configured to redirect at least a portion of the lightreceived from the light source via total internal reflection. Forexample, in some such embodiments, each of the lenses includes an inputsurface, an output surface and a lateral surface that extends betweenthe input and the output surfaces, where the lateral surface of at leastone of the lenses is configured to reflect the light from the sourceincident thereon via total internal reflection.

In some embodiments of the above optical system, the input surface ofthe central lens is a convex surface adapted to collimate light (i.e.,it generates a set of substantially parallel light rays) it receivesfrom the light source and each of the outer lenses includes a concaveinput surface configured as a section of a putative sphere centered onthe light source.

In other aspects, a kit is disclosed that includes a plurality of lensesconfigured to removably and replaceably couple to one another to form alens assembly configured to receive light from a light source. Thelenses of the lens assembly are arranged relative to one another suchthat such that each of the lenses can receive at input surface lightemitted by the source into an angular subtense different from arespective angular subtense associated with another lens. In someembodiments, at least one of the lenses guides at least a portion of thereceived light to its output surface via total internal reflection at alateral surface that extends between the input surface and the outputsurface.

Various features of each embodiment described above can be combined withone or more features of the other embodiments. Further understanding ofvarious aspects of the invention can be obtained by reference to thefollowing detailed description in conjunction with associated drawings,which are described briefly below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A schematically depicts a cross-sectional view of a lens assemblyaccording to an embodiment of the invention,

FIG. 1B schematically depicts exemplary ray traces through some lensesof the lens assembly of FIG. 1A,

FIG. 2A is an elevation view of the lens assembly of FIG. 1A depictingits output surface,

FIG. 2B is an elevation view of the lens assembly of FIG. 1A depictingits input surface,

FIG. 3A is a view of the output surface of the lens assembly of FIG. 1A,

FIG. 3B is a view of the input surface of the lens assembly of FIG. 1A,

FIGS. 4 and 5 schematically depict one way of assembling the lenses of alens assembly according to an embodiment of the invention,

FIG. 6 is a schematic cross-sectional view of a lens assembly accordingto another embodiment of the invention,

FIG. 7A is an exemplary distribution pattern of light exiting a lensassembly based on an implementation of the embodiment of FIG. 6,

FIG. 7B shows the light intensity along the y-axis of the distributionpattern shown in FIG. 7A,

FIG. 7C shows the light intensity along the x-axis of the distributionpattern shown in FIG. 7A,

FIG. 8 is a schematic cross-sectional view of another lens assemblyaccording to another embodiment of the invention,

FIG. 9 is a schematic cross-sectional view of another lens assemblyaccording to another embodiment of the invention,

FIG. 10A is an exemplary distribution pattern of light exiting a lensassembly based on an implementation of the embodiment of FIG. 9,

FIG. 10B shows the light intensity along the y-axis of the distributionpattern shown in FIG. 10A,

FIG. 10C shows the light intensity along the x-axis of the distributionpattern shown in FIG. 10A,

FIG. 11 is a schematic cross-sectional view of another lens assemblyaccording to another embodiment of the invention,

FIG. 12A is an exemplary distribution pattern of light exiting a lensassembly based on an implementation of the embodiment FIG. 11,

FIG. 12B shows the light intensity along the y-axis of the distributionpattern shown in FIG. 12A,

FIG. 12C shows the light intensity along the x-axis of the distributionpattern of FIG. 12A,

FIG. 13 is a schematic cross-sectional view of another lens assemblyaccording to another embodiment of the invention,

FIG. 14A is an exemplary distribution pattern of light exiting animplementation of the lens assembly of FIG. 11 without the lens cap,

FIG. 14B is another example of distribution pattern of light exiting animplementation of the lens assembly of FIG. 11 without the lens cap,

FIG. 14C is another example of distribution pattern of light exiting animplementation of the lens assembly of FIG. 11 without the lens cap, and

FIG. 15 is a schematic cross-sectional view of a lens assembly accordingto another embodiment of the invention.

DETAILED DESCRIPTION

The present invention is generally directed to a lens assembly (hereinalso referred to as an optic) that includes a plurality of lensesarranged to receive light from a light source such that each lensreceives at its input surface light emitted by the source into adifferent angular subtense associated with that lens. Each lens isconfigured to redirect at least a portion of the received light to anoutput surface via total internal reflection (TIR), or in some cases viaspecular reflection. In many embodiments, an airgap can separate lateralsurfaces of adjacent lenses to allow those surfaces to function as TIRsurfaces for redirecting, e.g., collimating, the light incident thereon.This in turn allows achieving a high level of redirection (collimation)while keeping the height of the lens assembly at a desired level. Thelens assemblies according to various embodiments can be used in avariety of lighting applications, and particularly in those in whichmechanical geometry requires minimal optic height and a high level ofcollimation. For example, they can be particularly useful inapplications in which large light emitting diodes (LEDs) are employed.

The phrase an “angular subtense” is used consistent with its meaning inthe art. For example, an angular subtense associated with a lens refersto a region of space defined by a solid angle that has its apex at thelight source and that subtends an input surface of the lens (See, e.g.,FIG. 1B).

The terms “about” is used herein to mean a deviation of at most 5percent, e.g., between 1 and 5 percent, in a value.

The phrase “substantially orthogonal” as used herein refers to an angleof 90 degrees within a deviation of at most 5-degrees, e.g., 1, 2 or5-degrees.

The phrase “substantially parallel to the optical axis” as used hereinrefers to a direction that is parallel to the optical axis with adeviation, if any, of at most 5-degrees from parallelism.

FIGS. 1A, 1B, 2A, 2B, 3A and 3B schematically depict a lens assembly 10according to an embodiment of the invention that includes a plurality oflenses 12, 14, 16, 18, 20, and 22 (herein collectively referred to aslenses 24) that are adapted to receive light emitted from a light source26. In this embodiment, the lenses 24 are rotationally symmetric aboutthe optical axis OA, which coincides with the optical axis of the lightsource 26. In this embodiment, the lens 12 is a central lens that iscircumferentially surrounded by annulus-shaped lenses 14, 16, 18, 20,and 22 (herein referred to collectively as the outer lenses), which aredisposed progressively at greater radial distances from the optical axis(OA) (the radial distance refers to a distance perpendicular to theoptical axis). In other embodiments, the optical axis of the lenses,e.g., an axis about which the lenses exhibit a rotational symmetry, maybe offset relative to a respective optical axis of the light source.Further, in some embodiments, one or more of the lenses may not berotationally asymmetric.

In this embodiment, the lenses are arranged relative to one another suchthat each lens receives light emitted by the source into a differentangular subtense (solid angle). By way of example, with reference toFIG. 1B, in this embodiment, the central lens 12 receives light emittedby the light source into an angular subtense γ while the lenses 18 and22 receive light emitted by the source into different angular subtensesα and β, respectively. In this manner, the lenses collectively receivelight emitted by the source into different solid angles. In someembodiments, the lenses collectively receive at least about 80 percent,or at least about 85 percent, or at least about 90 percent, or at leastabout 95 percent, or 100 percent, of the light energy emitted by thesource.

As discussed in more detail below, each of the lenses 24 includes aninput surface for receiving light from the light source and an outputsurface through which light exits the lens and a lateral surface thatextends between the input surface and the output surface. At least aportion of the light that is coupled into the lens body via the inputsurface is incident on the lateral surface so as to be totallyinternally reflected at that surface toward the output surface forexiting the lens. In this manner, the lens assembly 10 redirects, e.g.,collimates, via total internal reflection at least a portion of thelight it receives.

By way of example, the lens 14 includes an input surface 14 a, an outputsurface 14 b, and a lateral surface 14 c that extends between the inputsurface 14 a and the output surface 14 b. In this embodiment, the inputsurface 14 a is a concave surface that is shaped as a section of aputative sphere centered at the light source such that the light fromthe source (i.e., the light emitted by the source into the angularsubtense associated with the lens 14) is incident thereon in asubstantially orthogonal direction (as discussed below, in thisembodiment, the input surfaces of the other lenses 16, 18, 20, and 22are also shaped as sections of the putative spherical surface centeredon the light source). In this manner, the light enters the lens withoutmuch deviation from its propagating direction to be incident on thelateral surface 14 c. The lateral surface 14 c is separated from arespective lateral surface of adjacent lenses 12 and 16 by airgaps 1 and2. As air has an index of refraction that is lower than that of thematerial forming the lenses, the lateral surface 14 c can be configuredin a manner known in the art to cause total internal reflection of thelight incident thereon, or at least a portion of that light (e.g., atleast about 80% or 90%, or 100%). In this embodiment, the lateralsurface is configured to collimate the light incident thereon via TIRalong a direction that is substantially parallel to the optical axis(OA) (i.e., parallel to the optical axis (OA) within a deviation of atmost 5-degrees, e.g., 1, 2, or 5 degrees). The collimated light thenexits the lens through the output surface 14 b, which is substantiallyflat and orthogonal to the optical axis OA. In other embodiments, one orboth of the input and output surfaces 14 a and 14 b can have othershapes.

In this embodiment, the lenses 16, 18, 20 and 22 also include concaveinput surfaces (e.g., input surface 20 a of the lens 20) that areconfigured as sections of a putative sphere centered on the light sourceso as to be substantially orthogonal to the light incident thereon, andfurther include flat output surfaces (e.g., the output surface 20 b ofthe lens 20) that are substantially orthogonal to the optical axis (OA).In these lenses, the outer segment of the lateral surface (e.g., theportion 22 co of the lateral surface 22 c of the lens 22) can be formedof two portions that form an angle relative to one another (e.g.,portions 22 coi and 22 coii, where the segment 22 coii does notparticipate in light redirection) so as to ensure that the input surfaceis substantially orthogonal to the light it receives from the lightsource. Similar to the lens 14, the lateral surfaces of these lenses arealso separated by airgaps from lateral surfaces of adjacent lenses andare configured to redirect incident light via TIR.

In contrast to the outer lenses, the inner central lens 12 includes agenerally convex curved input surface 12 a that substantially collimatesthe light it receives from the light source via refraction to redirectthat light to its flat output surface 12 b, which is orthogonal to theoptical axis (OA), for exiting the lens. While the outer lenses redirectthe received light substantially via TIR for exiting their outputsurfaces in a direction substantially parallel to the optical axis, theinner lens redirects the received light substantially via refraction(e.g., refraction at its input surface) for exiting its output surfacein a direction parallel to the optical axis. In this manner, the lensassembly collectively collimates the light received from the source. Itshould be understood that some light rays may strike the lateral surfaceof the inner lens 12 to be reflected via TIR (an airgap separates thelateral surface of lens 12 relative to that of lens 14).

In other embodiments, the central lens 12 can be configured to redirectthe received light, e.g., to collimate the received light, primarily viaTIR, e.g., in a manner discussed above in connection with the outerlenses.

With reference to FIG. 1B, the lens assembly 10 can have an aspect ratioequal to or less than about 1, e.g., in a range of about 0.1 to about 1,where the aspect ratio is defined herein as the ratio of the height (H)of the assembly (in this case, the linear extent of the lens assemblyalong the optical axis OA) relative to the largest linear dimension of aputative surface that comprises all the output surfaces of the lensesand airgaps, if any, separating them; in this case, the diameter (D). Inmany embodiments, this aspect ratio allows an efficient redirection,e.g., collimation, of the light emitted by the source, particularly alarge source such as a large LED, while ensuring that the height of thelens assembly remains below a desired value. In particular, a putativeparabola (a geometry most associated with light collection) centered onthe light source and having a similar diameter D of the optic's aperturewould have an aspect ratio, as defined above, that can be represented bythe following mathematical relation:

${{Aspect}\mspace{14mu} {ratio}} = \frac{{Bx}^{2} + C}{x}$

where x denotes the radius of the aperture (x=D/2), and B and C areconstant.

The above relation shows that as x increases, the aspect ratio of such aputative parabola increases rapidly such that it would be greater than 1in many practical applications. In contrast, the lens assembly accordingto the invention can provide redirection (e.g., collimation) performancethat is at least equal to, and in many cases better than, the respectiveperformance of such a parabolic reflector while exhibiting a smalleraspect ratio, e.g., an aspect ratio less than 1.

The lenses 24 can be made from a variety of different materials. Someexamples of such materials include, without limitation, poly methylmethacrylate (PMMA), poly methyl methacrylimide (PMMI), cyclic olefincopolymer (COC), among others. In some embodiments, each of the lenses24 can be molded individually (e.g., via injection molding) and thenassembled. Many manufacturing methods are available for assembling thelenses. Some examples of such methods include, without limitation,ultra-sonic welding, gluing, heat-stacking, snap fitting, force fitting,etc.

As noted above, the lenses 24 of the lens assembly 10 can be fixatedrelative to one another in a variety of different ways. By way ofexample, FIGS. 4 and 5 schematically depict one way of stacking three ofsuch lenses and fixating them relative to one another such that airgapsseparate lateral surfaces of adjacent lenses. In particular, in thisexample, an outermost lens 30 includes a central cavity into which alens 32 can be inserted. The lens 32 includes a shoulder 32 asurrounding its output surface that can be seated in a recess 30 a ofthe lens 30 such that an airgap separates the lateral surfaces of thelenses 30 and 32. A central lens 34 can then be received by a centralcavity of the lens 32. Again, a shoulder 34 a of the lens 34 can beseated in a recess 32 b of the lens 32 such that the lateral surfaces ofthe two lenses are separated by an airgap. A retaining ring 36 can thenhold the lenses in place.

In some embodiments, the output surfaces of one or more of the lensescan include a textured surface, e.g., a plurality of microlenses, toalter the light incident on the output surface(s), e.g., the collimatedlight, to achieve specific beam angles.

In some embodiments, the lenses 24 of the lens assembly 10 can beselectively removable and/or replaceable so as to allow theconfiguration of the lens assembly 10 to be altered so as to control thefar-field illumination pattern, for example. For example, each of thelenses can be removed and replaced independent of the other lenses,i.e., without a need to remove any of the other lenses.

Additionally or alternatively, a lens cap can be configured to couple tothe output end of the lens assembly 10 for altering (e.g., diffusing)the light exiting the lens assembly 10 and/or preventing a person fromreceiving light directly from the light source. In such a manner, theuser can selectively couple the lenses and/or lens cap in variouscombinations such that the lens assembly 10 produces a specified beamangle or far-field illumination pattern.

For example, with reference now to FIGS. 6-13, an exemplary lightingassembly 10 is depicted in which various lenses can be selectivelycoupled to one another and/or to which a lens cap 40 can be selectivelyapplied so as to control the distribution of light exiting the lensassembly 10. With specific reference first to FIG. 6, the exemplarylighting system 10 includes an annular outer lens 30 defining a centralcavity 42 and having two annular recesses 30 a,b surrounding the centralcavity adjacent the output end of the outer lens 30, for example, asdescribed above with reference to FIGS. 4 and 5. As shown in FIG. 6,however, a lens cap 40 can be configured to be disposed within therecess 30 a and across the central cavity such that light emitted by thesource through the central cavity 42 is diffused by the lens cap 40. Assuch, a user can configure the lens assembly 10 as shown in FIG. 6 toproduce a very wide beam far-field distribution pattern (e.g., a floodpattern), e.g., such as that depicted in FIGS. 7A, 7B, and 7C.

The lens cap 40 can have a variety of configurations so as to controlthe distribution of light. By way of example, the lens cap 40 can have atextured surface, e.g., a plurality of microlenses, to alter the lightincident on the lens cap 40 to achieve specific beam angles. Rather thanrest within the recess 30 a, it will be appreciated that the lens cap 40can alternatively be coupled to the lens assembly such that lightexiting the output surface of the outer lens 30 also passes through thelens cap 40, as depicted in FIG. 8, for example.

With reference now to FIG. 9, in another exemplary configuration of thelens assembly 10, the lens cap 40 of FIG. 6 can be removed and replacedwith an inner lens 34 having a shoulder 34 a configured to engage therecess 30 a of the outer lens 30 (alternatively, the lens cap 40 of FIG.8, can be disposed on or coupled to the output surface of both the outerlens 30 and inner lens 34). As discussed otherwise herein, the inputsurface, the output, and the lateral surfaces of the inner lens 34 canbe configured so as to control the beam angle of the light exiting theoutput surface of the inner lens 34. In such a manner, the user cangenerate a wide beam output via the light exiting the outer lens 30 andinner lens 34, for example, as depicted in FIGS. 10A, 10B, and 10C. Itwill further be appreciated that in some embodiments, the shoulder 34 aof the inner lens 34 can diffuse the light impinging thereon from thesource or have a textured surface (e.g., a microlens array) so as tocontrol the distribution of light exiting therefrom.

With reference now to FIG. 11, another exemplary configuration of thelens assembly 10 is depicted which can be used to provide a medium beamlens that can produce, e.g., the exemplary light distribution depictedin FIGS. 12A, 12B, and 12C. The configuration of the lens assembly 10 inFIG. 11 is like that depicted in FIG. 9 but differs in that a middlelens 32 is disposed within the central cavity and between the outer lens30 and the inner lens 34. As will be appreciated by a person skilled inthe art, the middle lens 32 can also include a shoulder 32 a and can bedimensioned so as to engage the recess 30 b of the outer lens 30, withthe shoulder 34 a of the lens 34 extending over the middle lens 32 andremaining in engagement with the recess 30 a of the outer lens.

Similar to the discussion above in which the inner lens 34 and middlelens 32 can be selectively replaced, the outer lens 30 can also beremovable and replaceable in the lens assembly 10 so as to control theoutput pattern of light. By way of example, the outer lens 30 can bereplaced by one of a similar size but having different outputcharacteristics so as to generate a more narrow beam (e.g., without amicrolens array on its output surface). Alternatively, the lens cap 40described above with reference to FIG. 8, which can be disposed over theouter lens 30, middle lens 32, and inner lens 34 (i.e., medium beampattern) as shown in FIG. 13, can be removed as shown in FIG. 11 suchthat the output beam becomes narrow, for example, as depicted in FIGS.14A, 14B, and 14C.

It will thus be appreciated in light of the present teachings that thereexits many variations and configurations for the output surfaces of thevarious lenses and their nesting configurations with or without a lenscap 40 that can be used to tailor the output of the lens assembly 10 toa particular application.

Further, in some embodiments, one or more of the lenses can employspecular reflection, rather than total internal reflection, forredirecting, for example, collimating, at least a portion of the lightreceived from the light source. For example, in some such embodiments,at least a portion (and in some cases the entire) lateral surface of oneor more of the lenses can be metalized to provide specular reflection ofthe light incident thereon. In some embodiments, a combination ofspecular and total internal reflection can be employed for redirectingthe light received from the light source.

By way of example, FIG. 15 schematically depicts a lens assembly 10′according to another embodiment of the invention that includes aplurality of lenses 12′, 14′, 16′, 18′, 20′ and 22′ arranged in a fixedrelationship relative to one another to receive light from the lightsource 26. Similar to the lens assembly 10 discussed above, each of thelenses of the lens assembly 10′ is configured and positioned relative tothe light source so as to receive light emitted by the source into adifferent solid angle (angular subtense). While the lenses in the lensassembly 10 rely on total internal reflection to redirect at least someof the received light, the lenses in the lens assembly 10′ rely onspecular reflection for redirecting at least a portion of the receivedlight. In particular, at least a portion of the lateral surface of eachof the lenses of the lens assembly 10′ is metalized (e.g., a thin metallayer having a thickness in a range of about 10 micrometers (μm) toabout 100 μm is deposited on the surface) to provide a reflectivesurface for redirecting the incident light to the output surface. Inthis embodiment, the lenses 12′, 14′, 16′, 18′, 20′ and 22′ include,respectively, thin metal coatings 12′a, 14′a, 16′a, 18′a, 20′a, and 22′aon at least a portion of their lateral surfaces for reflecting andthereby redirecting at least a portion of the received light. In somesuch embodiments, the use of metal coating obviates the need to haveairgaps between the lateral surfaces of adjacent lenses and hence allowsthose surfaces to be in contact with one another.

Those having ordinary skill in the art will appreciate that variouschanges can be made to the above embodiments without departing from thescope of the invention. For example, the output surface of the lensassembly (e.g., a putative surface comprising the output surface of thelenses of the lens assembly and airgaps, if any, separating the lenses)can have a shape other than circular, such as square, rectangular,elliptical, etc.

1. An optical lens assembly, comprising a plurality of lenses adapted toreceive light from a light source, each of said lenses having an inputsurface and an output surface and a lateral surface extending betweensaid input surface and output surface, said lenses being arrangedrelative to one another such that each of the lenses receives at itsinput surface light emitted by the source into an angular subtensedifferent than a respective angular subtense associated with anotherlens, wherein each of said lenses guides at least a portion of thereceived light to its output surface via total internal reflection atthe lateral surface thereof.
 2. The optical lens assembly of claim 1,wherein at least one of said lenses is configured to collimate at leasta portion of the light it receives from the light source.
 3. The opticallens assembly of claim 1, wherein the lateral surfaces of at least twoadjacent lenses of said lens assembly are separated from one another byan airgap.
 4. The optical lens assembly of claim 1, wherein said lensesare configured to collectively receive at least about 80% of the lightemitted by said light source.
 5. The optical lens assembly of claim 1,wherein said lenses are configured to collectively receive at leastabout 90% of the light emitted by said light source.
 6. The optical lensassembly of claim 1, wherein said lens assembly exhibits an aspect ratioless than about
 1. 7. The optical lens assembly of claim 1, wherein theinput surface of at least one of said lenses is configured such that thelight from the light source incident thereon is substantially orthogonalthereto.
 8. The optical lens assembly of claim 1, wherein at least ofsaid lenses exhibits a flat output surface.
 9. The optical lens assemblyof claim 1, wherein the plurality of lenses comprises an inner lens, amiddle lens, and an outer lens.
 10. The optical lens assembly of claim9, wherein the plurality of lenses are removably and replaceably coupledto one another.
 11. The optical lens assembly of claim 1, wherein eachof said lenses is selectively removable and replaceable independent ofthe other lenses.
 12. The optical lens assembly of claim 1, furthercomprising a lens cap configured to receive light from one or more ofthe output surfaces of the plurality of lenses.
 13. The optical lensassembly of claim 12, wherein said lens cap comprises a texturedsurface.
 14. The optical lens assembly of claim 12, wherein said lenscap comprises a plurality of microlenses.
 15. The optical lens assemblyof claim 12, wherein said lenses are fixedly coupled to one another witheach lens disposed in a cavity of an adjacent outer lens.
 16. Theoptical lens assembly of claim 15, further comprising a retaining ringfor fixating the lenses in a defined relationship relative to oneanother.
 17. The optical lens assembly of claim 15, wherein at least oneof said lenses comprises an annular shoulder seated in an annular recessof an outer adjacent lens such that a lateral surface of said at leastone lens is separated by a gap from a respective lateral surface of saidouter adjacent lens.
 18. The optical lens assembly of claim 16, whereinat least one of said lenses comprises a lateral surface configured toredirect light incident thereon via specular reflection.
 19. The opticallens assembly of claim 18, wherein said lateral surface providingspecular reflection is metalized.
 20. The optical lens assembly of claim19, wherein said metalized surface comprises a metal layer having athickness in a range of about 10 micrometers to about 100 micrometers.21. An optical system, comprising a light source, an optical lensassembly optically coupled to the light source to receive lighttherefrom, said optical lens assembly comprising a central lens, and aplurality of outer lenses disposed about the central lens, wherein thelenses of the optical lens assembly are arranged relative to one anotherand relative to the light source such that each lens receives lightemitted by the source into a different angular subtense.
 22. The opticalsystem of claim 21, wherein the outer lenses are annulus shaped lensesthat circumferentially surround the central lens at progressivelyincreasing radial distance from the central lens.
 23. The optical systemof claim 21, wherein said optical lens assembly is configured toredirect at least a portion of the light received from the light viatotal internal reflection.
 24. The optical system of claim 21, whereineach of the lenses of the optical assembly comprises an input surface,an output surface and a lateral surface that extends between the inputand the output surface.
 25. The optical system of claim 23, wherein thelateral surface of at least one of said lenses is configured to reflectlight incident thereon via total internal reflection.
 26. The opticalsystem of claim 21, wherein the input surface of said central lens is aconvex surface adapted to collimate light it receives from the lightsource.
 27. The optical system of claim 26, wherein each of said outerlenses comprises a concave input surface configured as a section of aputative sphere centered on the light source.
 28. The optical system ofclaim 21, wherein the lateral surface of each of said lenses isseparated by a gap from a lateral surface of an adjacent lens.
 29. Theoptical system of claim 21, wherein said lenses are removably andreplaceably coupled to one another.
 30. The optical system of claim 21,wherein said optical lens assembly has an aspect ratio in a range ofabout 0.1 to about
 1. 31. A kit, comprising a plurality of lensesconfigured to removably and replaceably couple to one another to form alens assembly configured to receive light from a light source, whereinthe lenses of the lens assembly are arranged relative to one anothersuch that each of said lenses can receive at it input surface lightemitted by the source into an angular subtense different from arespective angular subtense associated with another lens.
 32. The kit ofclaim 31, wherein at least one of the lenses guides at least a portionof the received light to its output surface via total internalreflection at a lateral surface thereof extending between the input andthe output surface.